In New York state, these insects are annual nesters. Every spring, reproductive females start nests in small ground depressions and cavities. The only evidence of such a nest is a small ground-level entrance.

Yellow jacket nests are usually not discovered until their populations are near their peak in late August and September. Disturbing a nest at this stage can be quite unpleasant and even dangerous.

We identify these large yellow jacket wasps on our helpline each autumn. A simple explanation is that yellow jackets are more noticeable in fall because there are more of them. By the time we notice that wasps are a problem, the colony has grown to huge proportions. Yellow jacket nests at this time of year can number in the thousands and sometimes become a nuisance in backyards and picnic areas.

Yellow jackets capture flies and other insects to feed their young, and are pollinators in your garden. If they are not posing any danger where they are, it is best to leave them alone.

If the location of the nest poses a danger, wasp and hornet sprays can be purchased at your home and garden stores. The insecticide sprays are most effective when applied in the early evening when all the individuals are in the nest. Cool temperatures (below 60 degrees F) are also helpful since they slow nest activity. Examine the nest during the daytime so that you will be familiar with its location that evening.

The aerosol sprays differ in their effective range, so always read the directions. Spray directly into the entrance hole of the wasp nest for maximum effect. If the insects begin to emerge from the nest, simply walk away from the area and return later. Remember to watch for stunned or dying insects on the ground. Patience will prevent accidents.

Two insecticide applications are best for yellow jacket nests. The second spraying should be performed about one hour after the first. If you are uneasy about this, it would be best to call an exterminator.